Heading machines

ABSTRACT

A machine for producing headed blanks from wire stock in which continuous wire stock is fed through a reciprocating ram by means of reciprocating gripper jaws which are adjustable for position and feed length and which are cam urged into engagement with the wire at a specific instant in the machines cycle. The heading machine includes a die block containing a plurality of dies which can be rotatably indexed. The free end of the wire passes through a bush in a cut-off mechanism and into a die cavity disposed at a cut-off station, whereupon an open knife is urged against the wire to sever a blank which is left in the die cavity, the die block then being indexed to subsequent stations where a heading operation is done. Each cavity of the die block has an ejector and all the ejectors are coupled for longitudinal adjustment so that individual adjustment is not required in use.

United States Patent 1 91 1111 3,919,874

Harris Nov. 18, 1975 [5 HEADING MACHINES 3.844.152 10/1974 Peytavin 72/291 [75] inventor: Lewis Nigel Harris, Stourbridge,

E l d Primary E.\'aminerC. W. Lanham Assistant E.raminerJames R. Duzan ['73] Asslgnee: g gfiei g l j Llmltedi Attorney, Agent, or FirmFriedman & Goodman n an [21] Appl' 480036 A machine for producing headed blanks from wire stock in which continuous wire stock is fed through a 52 us. c1 72/337; 10/11 R; 10/13; reciprocating ram y means of reciprocating grippcr 72 2 7 jaws which are adjustable for position and feed length 51 Int. c1. B21D 28/00 and which arc cam urged into engagement with the [58] Fi ld f S h M 10/11 R, 1 E, 12 R, 25 wire at a specific instant in the machines cycle. The 10/13 15; 72/337 33 31g 29 297 2 7 heading machine includes a die block containing a 283 239 290 291; 22 /112 1 4 1 3 plurality of dies which can be rotatably indexed. The free end of the wire passes through a bush in a cut-off [56] References Ci d mechanism and into a die cavity disposed at a cut-off UNITED STATES PATENTS station, whereupon an open knife is urged against the wire to sever a blank which is left in the die cavity, the weeks 10/13 die block then being indexed to subsequent stations 226l'066 10/1941 where a heading operation is done. Each cavity of the 237683394 10/1956 die block has an e ector and all the 6J6Ct0l'8 are cou- 2,786,217 3/1957 pled for longitudinal adjustment so that individual ad- 3,158,047 1 l 1964 justment is not required in use. 5183; 4 Claims, 17 Drawing Figures US. Patent Nov. 18,1975 sheetlof 15 3,919,874

U..S.-Pat@m N0v.18, 1975 Sheet30f 15 3,919,874 I US, Patent Nov. 18, 1975 Sheet4 of 15 3,919,874

U.S-. Patent Nov. 18, 1975 ShaetSof 15 3,919,874

FIG.

US. Patent N0v.18, 1975 Sheet6of 15 3,919,874

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US. Patent Nov. 18,1975 Sheet8of 15 3,919,874

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U.S.Patent Nov. 18 1975 Sheet90f15 3,919,874

US. Patent Nov. 18, 1975 Sheet 10 0f 15 3,919,874

vHI. II v U.S Patent Nov. 18, 1975 Sheet11of15 3,919,874

US. Patent Nov. 18, 1975 Sheet 12 of 15 3,919,874

US. Patent Nov. 18 1975 Sheet 13 of 15 3,919,874

US. Patent Nov. 18, 1975 Sheet 15 of 15 HEADING MACHINES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a heading machine for producing headed blanks from wire stock.

In a heading machine, a continuous long length of wire stock is fed to the machine and a short length is severed from the stock to form a blank which is acted upon by the machine to enlarge one end of the blank to form a head.

The invention is concerned with the type of heading machine in which a reciprocating ram carries one or more punches co-operable with a die assembly having a number of dies. The basic operation in this type of machine is that a blank which has been severed from the wire stock is held in a die and a punch on the reciprocating ram acts on the projecting end of the blank to form a head. Reference to a heading machine of the type specified is hereinafter to be taken as meaning the type of machine set out in this paragraph.

A heading machine of the type specified may be used for example for producing headed blanks intended to be made into screws and may have two or even more punches. The die assembly would comprise a number of dies mounted in the machine in such a way that the dies can be indexed round from one station to another so that a blank in one die would be acted upon by a first punch to produce a preliminary head and then the die would be indexed round to bring it into line with a second punch which would operate upon the so formed preliminary head, and so on, until the final desired form of head has been produced.

2. Description of the Prior Art A conventional heading machine of the type specified has hitherto had a number of disadvantages, which stem from various aspects of the operation of the machine and, so that the present invention can more readily be understood, a brief description of a conventional heading machine will now be given.

Wire stock is fed longitudinally alongside the machine in a direction parallel to the direction of reciprocation of the ram. The stock moves forwardly under the action of feed rollers until its free end abuts a stop. A cutting tool in the form of an open knife is then used to sever a blank from the end of the stock, the spacing of the knife from the stop determining the length of the blank. Transfer mechanism associated with the cutting tool then moves the severed blank transversely to a position in which it is in line with a die in the die assembly and the oncoming punch pushes the wire out of the transfer mechanism and into the die.

Where the cutting tool is an open knife, the transfer mechanism is usually a finger controlled by cam or spring means which grips the wire during transfer of the blank to to the die. The knife and finger are then rapidly retracted to avoid the oncoming punch.

The headed blank is ejected from the die by ejector means.

The conventional heading machine described above has various disadvantages.

The feed rollers used to feed the wire stock longitudinally comprise a pair of grooved rolls which are spring urged into engagement with the wire and are rotated intermittently in one direction to advance the stock. The dimensions of the groove in each feed roll are slightly larger than the dimensions of the wire, in order to avoid pinching and hence deforming the wire during feeding. Taking into consideration the curvature of the feed rolls, it will be seen that there is virtually point contact between each roll and the wire and it is therefore necessary to regulate the spring loading of the rolls very carefully to avoid deforming the wire. However, if the spring loading is too light, the rolls may slip slightly and the amount of wire fed forwardly is then shorter than the desired length. This problem is usually tackled by overfeeding. The rotation of the rollers is arranged so as to be theoretically capable of feeding forward rather more than the desired length of wire stock, assuming that the rolls do not slip, and the stock is fed up to a fixed stop so as to prevent any further wire being fed forwardly. This inevitably means that the rolls must slip on the wire and this can lead to marking of the wire and subsequent cracking of the headed blanks produced from the wire stock.

Once the wire has been fed up to the stop, there are further disadvantages which stem from the fact that it is not in line with the die and that the wire must be cut and the blank transferred to the die. When an open knife is used to cut the blank, this can lead to the for mation of a poor quality blank owing to the wire being bent prior to being cut. The blank may also be scored by the knife either at the stage where the wire is being fed to the knife or at the stage where the cut-off blank is being fed into the die. The transfer mechanism and knife must be moved very quickly out of the way of the oncoming punch and this rapid movement leads to wear of the component parts of the system, high inertia forces and, unless very great care is taken, it is possible for the transfer finger in particular to foul the oncoming punch. This problem becomes most acute when the blanks being operated on are ofa relatively short length since the punch is very close to the die assembly when it first contacts the blank and this leaves very little time or space for the retraction of the transfer mechanism.

In general, the conventional machine described above tends to be rather difficult to set up because a number of relatively tedious and time consuming adjustments have to be made to the setting and timing of the machine if the length of blank required is altered, for example.

BRIEF SUMMARY OF THE INVENTION Bearing in mind the disadvantages mentioned above, the present invention has an object the provision of a simplified heading machine which is capable of producing good quality headed blanks and which minimizes or overcomes at least some of the above-mentioned disadvantages.

According to the invention there is provided a heading machine of the type specified wherein wire stock is fed intermittently and by controlled amounts linearly through the ram directly into a die at a cut-off station, and is thereacted upon by a cut-off mechanism to sever a blank therefrom and the die containing the blank is then indexed in a direction perpendicular to the wire stock to a punching station where it is acted upon by a punch carried by said ram.

The wire stock may be fed by a feeding mechanism comprising opposed linear gripper means which can embrace and grip the wire over a substantial length thereof, said gripper means being mounted in the machine for rectilinear movement back and forth in the direction of movement of the ram, drive means being provided for driving the gripper means back and forth 3 and means also being provided for engaging and releasing the gripper means at the beginning and end respectively of a forward feed movement of the wire stock.

The wire cut-off mechanism may comprise, in combination, a wire supporting bush through which the wire is fed and which is located adjacent the die at the cutoff station, and an open knife located between the bush and the die and spaced from the face of the die, operation of the cut-off mechanism severing the wire to leave a blank in the die with a portion of the blank projecting from the face of the die.

The machine may have an ejector mechanism associated with the die assembly, such that each die has a re spective ejector rod, each ejector rod being slidably mounted in a common mounting member and being spring urged rearwardly to bring a fixed projection on the rod into load transmitting relationship with the mounting member, the mounting member being capable of fore and aft rectilinear adjustment relative to the die block into which the ejector rods extend.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings which show one heading machine embodying the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is an isometric view of the complete machine with certain cover plates removed to expose parts of the mechanism,

FIG. 2 is an isometric view similar to that of FIG. 1 but with further parts broken away to show interior details of the mechanism,

FIG. 3 is an isometric view of an enlarged scale of the feed mechanism for the machine,

FIG. 4 is an isometric view, on a different scale, of an operating mechanism associated with the feed mechanism,

FIG. 5 is a plan view of part of the machine giving further details of the feed mechanism,

FIG. 6 is a sectional view on the line 66 of FIG. 5,

FIG. 7 is an enlarged sectional view on the line 77 of FIG. 5 showing drive means for the feed mechanism,

FIG. 8 is an enlarged isometric view of a cut-off mechanism, with certain parts broken away to show the operation of the machine,

FIG. 9 is an isometric view on a different scale of an indexing means used for indexing the die block of the machine,

FIG. 10 is a sectional view of the cut-off mechanism and its associated operating mechanism shown on a smaller scale,

FIG. 1 1 is a longitudinal section on the line 1111 of FIG. 10,

FIG. 12 is a slightly enlarged front elevational view of the cut-off mechanism shown in FIGS. 8, 10 and 11 and illustrating the way in which it is mounted in the body of the machine,

FIG. 13 is an enlarged sectional view of an adjustment means associated with the cut-off mechanism,

FIG. 14 is an enlarged sectional view of a further adjustment means associated with the cut-off mechanism,

FIG. 15 is a front elevational view of the die assembly of the machine,

FIG. 16 is a sectional view of the die assembly and associated ejector mechanism taken on the line l6l6 of FIG. 15 and showing the operating mechanism of the ejector system,

4 FIG. 17 is an enlarged sectional view of the die block and part of the ejector mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT GENERAL LAYOUT OF THE MACHINE The heading machine according to the invention is shown in general layout in FIGS. 1 and 2 of the drawings.

The main frame of the machine comprises parallel side frame member 20 and 21, between which is mounted a ram 22 which can reciprocate parallel to the frame members 20 and 21.

The drive to the machine is supplied by an electric motor 23 which drives a transverse crankshaft 24 via a belt 25. All the various operations carried out by the machine are provided with their drive either directly or indirectly from the crankshaft 24.

Along each side of the machine there is a secondary shaft driven from the main crankshaft 24 via an intermediate shaft 72. On the nearside of the machine as shown in FIGS. 1 and 2, there is the secondary shaft 26. A further secondary shaft 27 runs parallel to the secondary shaft 26 on the opposite side of the machine and can be seen in FIG. 4 of the drawings.

The secondary shaft 26 operates a cut-off mechanism whilst the secondary shaft 27 operates a feed mechanism.

A cross-shaft 28 extends generally parallel to the main crankshaft 24 but towards the opposite end of the machine and this cross-shaft 28, which can be seen in FIG. 9, provides the motive power to index a die assembly forming part of the machine.

Finally, a vertical shaft 29, which can be seen in FIG. 2 of the drawings, is driven from the cross-shaft 28 to operate an ejector mechanism.

The heading machine basically comprises a feed mechanism generally indicated at 30 which feeds a length of wire stock through the ram 22 and into a die cavity, the end of the wire stock then being cut off by a cut-off mechanism generally indicated at 31. The die cavity is disposed in a die block which is then indexed so as to bring the die cavity containing the blank into line with a punch provided on the ram 22 which carries out a heading operation.

When the desired head has been produced on the blank, an ejector mechanism generally indicated at 32 ejects the headed blank from the die and the blank then passes out of the machine, leaving the die cavity empty to be indexed back to the cut-off station to receive the free end of the wire stock prior to formation of another blank.

In common with many conventional machines, the die block includes a number of die cavities which are indexed between the various stations where operations are performed and adjacent die cavities contain blanks in different stages of manufacture.

It will be appreciated that the machine framework has been broken away somewhat in FIGS. 1 and 2 of the drawings and in particular the main working parts of the machine will in general be enclosed by a cover plate, one small portion of which is shown at 33.

The ram 22 is reciprocated on fixed guide rods 34. Suitable hydrostatic or hydrodynamic bearings may be provided for the ram and the various rotating shafts.

The feed mechanism If reference is made to FIGS. 3 to 7 of the drawings, these show the feed mechanism of the machine in more detail.

Referring to FIG. 3, the ram is indicated at 22 and it will be seen that the feed mechanism generally indicated at is disposed within or behind the operative face of the ram. Wire stock in a continuous long length is shown passing through the feed mechanism 30 and then through the ram 22 on its way to the region where the heading operation is performed.

The feed mechanism 30 broadly consists of a pair of gripper jaws 36 and 37, each of which has an arcuate gripping face which contacts the cylindrical outer surface of the wire 35 along a substantial length of the wire. The jaw 36 will be referred to as a fixed jaw whilst the jaw 37 will be referred to as a movable jaw, but it will be appreciated that in face both jaws of the feed mechanism 30 do in fact move relative to the framework of the machine in order to feed the wire stock 35 through the machine.

The feed mechanism is mounted on parts 38 which are secured to the underside of a plate 39 attached to a transverse beam 40 which is visible in FIG. 1 of the drawings and extends from side to side of the machine housing.

As seen more clearly in FIG. 6, a part of each gripper 36, 37 which actually engages the wire stock is in the form of a replaceable insert. Such inserts are small and can easily be replaced if the diameter of the wire stock needs to be varied. They can also be made of carbide or other suitable tough or hardwearing material if required for ensuring extra life.

Referring to FIGS. 3 and 6, the fixed gripper 36 is mounted in a block 41 which is slidably engaged in a slideway 42 formed in a block 43 carried by a bracket 44 on the plate 39. Suitable bearings such as needle roller bearings are provided in the slideway 42 for smooth sliding movement of the block 41.

Referring to FIGS. 5 and 7 in particular, a toothed rack 45 carried by the ram 22 drives a pinion 46 which is mounted on the feed mechanisms crankshaft previously referred to. The crankshaft 27 is carried in bearings fixed to the frame of the machine and the crankshaft 27 reciprocates the block 41 via a connecting rod 47, thus providing the reciprocating drive for the grippers.

The arrangement of the gripper drive is such that the grippers are driven by the ram but the use of a crankshaft enables the timing of the forward and backward movement of the grippers to be slightly delayed relative to that of the ram. The main crankshaft driving the ram may be 70 in advance.

The grippers are urged apart by a helical spring 48.

The fixed gripper, as referred to above, is mounted in the block 41, but the movable gripper is mounted on a pivotable lever block 49 which is pivoted on a pin 50 carried by a bracket rigid with the block 41. Thus, the movable and fixed jaws both reciprocate simultaneously but the movable jaws can be swung on the lever block 49 relative to the pivot pin 50. The movable gripper is spring urged towards the wire stock and has on its rear face a stem 51 slidably mounted in the lever block 49 and surrounded by spring washers such as Belleville washers 52 which provide the spring bias.

At the end of the lever block 49 which is remote from the pivot pin 50, there is a rotatable roller 53 which is 6 adapted to run along a fixed linear cam surface 54 which controls the movement of the movable gripper 37 towards and away from the fixed gripper 36 and hence controls the gripping and release of the wire for the intermittent feeding action.

The cam surface 54 has two parallel portions linked by a ramp 55. The grippers are brought together to grip the wire while the roller 53 is on the higher surface of the cam 54 and, as the grippers move forwardly carrying the wire stock, the roller 53 runs down the ramp 55 to the lower profile portion of the cam which immediately enables the movable gripper 37 to be spring urged away from the fixed stripper 36 by the spring 48, thus releasing the wire stock. From this, it will be seen that the longitudinal position of the ramp 55 predetermines the length of the feed travel of the grippers. Adjustment means are provided for adjusting this longitudinal position of the ramp 55 of the cam surface 54.

The cam 54 is withdrawn completely from the roller 53 during the time when the bar stock is not being fed forwardly and this is achieved by having the cam 54 pivotally mounted so as to be rockable between a position in which it engages the roller 53 and a position in which it is completely disengaged from the roller 53.

Referring particularly to FIGS. 5 and 6, the cam 54 is pivotally mounted relative to a shaft 56 and is linked to an operating rod 57 so that, at a particular time during the operating cycle of the machine, the rod 57 rocks the cam 54 into engagement with the roller 53 and at a later time the rod 57 rocks the cam away from the roller.

The linkage between the operating rod 57 and the cam 54 is provided by a further shaft 58 which is mounted in brackets 59 from the mounting plate 39. The shaft 58 carries a sleeve 60 which is keyed to the shaft and has a radially projecting lug 61 which rocks a block 62 on which the cam 54 is mounted. The shaft 58 has a radially extending arm 63 which is pivotally secured at 64 to the operating rod 57.

The feed of the wire commences when the block 62 is rocked in one direction to bring the cam 54 against the roller 53 and engage the grippers. When the grippers have moved along the cam 54 until the roller has run down the ramp 55, this relieves the feed and the block 61 is then rocked in the opposite direction to fully disengage the grippers so that there will be no drag on the wire as the grippers perform their return movement.

As mentioned above, longitudinal positional adjustment of the cam 54 determines the length of wire fed forward with each reciprocation of the grippers. The position of the cam 54 is adjusted by axial movement of the shaft 56. As referred to, the cam is mounted on a block 62 pivoted on the shaft 56 which is itself mounted on T-section member 65 movable in an undercut slideway 66.

The shaft 56 extends to the rear of the machine and is formed with a generally square cross-section part 67 which has rounded corners as shown. At the rearwardly extending part of the shaft 56 part thread formations 68 are provided on these rounded comers and are engaged by an internal thread provided on a rotatably mounted gear wheel 69 which is held against axial movement. Thus, rotation of the gear wheel 69 causes longitudinal movement of the shaft 56 and hence positional adjustment of the cam 54 in the longitudinal direction. A handwheel 70 rotates a shaft carrying a pinion 71 which has teeth engaging with the teeth of the gear 7 wheel 69. Thus, the handwheel 70 is used for adjusting the longitudinal position of the cam 54.

It has been described above how the grippers engage and disengage the wire stock 35, under the action of the operating rod 57. Referring now to FIG. 4 of the drawings, this broadly illustrates how the operating rod 57 is controlled from the secondary shaft 27 which runs along the far side of the machine as seen in FIGS. 1 and 2 and which is driven, via bevelled gearing 71, from an intermediate drive shaft 72 which can be seen in FIG. 2. This in turn is driven from the main crankshaft 24 of the machine through suitable gearing and also drives the secondary shaft 26 briefly referred to above.

The shaft 27 carries a pair of cams which operate on respective followers carried by arms mounted on the shaft 73 to produce rocking movement of a lever 74 which is pivotally connected to the end of the operating rod 57 by means of a pivot pin 75.

The position of the cams on the shaft 27 controls the timing of the complete feed mechanism and is set so that the grippers are stationary, considered in the axial direction of the wire, when they are actuated to grip the wire. Thus, the longitudinal cam 54 is rocked into position when the connecting rod 47 on the crankshaft 46a is at bottom dead centre prior to starting the forward travel of the gripper assembly.

The mechanism generally indicated at 76 in FIG. 4 is a known type of manually adjustable arrangement which prevents the grippers being engaged or disengaged except at a specific part of the cycle of operations when the feed is not normally operative, which prevents short feeding of the wire.

The cut-off mechanism The cut-off mechanism will now be described with reference to FIGS. 8 to of the drawings, although brief reference may be made to other figures.

As mentioned above, the cut-off mechanism is generally indicated at 31 in FIGS. 1 and 2. The wire stock 35 is fed by the gripper mechanism 30 into a cavity 77 of a die block 78, through a brush 79, in the manner shown in FIG. 8 of the drawings.

The die block 78 is shown in more detail in FIG. 15 and will be seen to include four die cavities 77, each of which is fitted with ejector means to be described in more detail later, the four die cavities being arranged symmetrically about an axis on which the die block can rotate.

The wire stock 35 is fed into a cavity 77 at a cut-off station where the wire is severed to leave a blank within and projecting from the cavity 77, whereupon the die block 78 is indexed around so that the cavity containing the blank is brought into line with a punch which acts on it at a first blow station to form a preliminary head. The die block is then further indexed to bring the blank to a second blow station where a finishing operation is carried out and is further indexed to an ejector station where the ejector mechanism ejects the headed blank from the cavity 77.

FIG. 1 shows the general layout of the machine and it can be seen that the cut-off mechanism 31 id disposed at an angle to the vertical and is mounted on a bracket 81 above the die block which cannot be seen in this figure.

Reference has already been 'made to the secondary shaft 26 which runs along the nearside of the machine as seen in FIGS. 1 and 2 of the drawings and it is this secondary shaft which operates the cut-off mechanism.

8 The indexing of the die block 78 is powered from the other secondary shaft 27 referred to above and shown in FIG. 4 of the drawings.

The free end of the wire stock 35 passes through the bush 79 which is mounted on an outer slide 82 in the cut-off assembly 31. Within the outer slide 82, there is an inner slide 83 which carried on open knife 84 having a curved cutting edge 85 which is of semi-circular shape so as to conform to the upper surface of the wire 35. The knife 84 is free of the wire as the stock is fed through the bush 79 into the die cavity 77.

The action of the cut-off mechanism 31 is such that the inner slide 83 is forced downwardly and the outer slide 82 is resiliently urged somewhat upwardly so that the knife 84 severs the wire stock 35 which is constrained by the bush 79 and is supported during the cutting operation.

In this way, the open knife 84 can be used to give a clean cut-off edge and, because the knife is kept free from the wire except during the actual cut-off operation, there is no tendency for the wire to become scratched or marked by the knife as it is fed into the die cavity 77. The cut-off edge of the wire is therefore sharp and, since the wire does not flex away from the knife during cutting, the edge is also square with respect to the axis of the wire. It will be appreciated that, although the bush 79 is urged somewhat upwardly, the forces exerted on the wire held therein are not sufficient to exceed the elastic limit of the wire so that it suffers no permanent deformation.

The cut-off action is operated by means of a toggle mechanism 86 which is extended by an operating rod 87, the position of which relative to the rest of the machine can be seen from FIG. 2.

Considering the cut-off mechanism 31 in more detail, the mechanism is housed in a housing 88 of generally channel section, the front of which is closed by a plate 89, and the channel section interior of which serves to mount the slides 82 and 83.

The slide 82 is normally urged downwardly by a spring 90 which is housed in a bore in the upper part of the housing 88. The bore also accommodates a threaded stud 91 which can be used initially to adjust the normal position of the slide 82 and hence the bush 79 relative to the wire stock 35 so that the bush is initially aligned with the die cavity.

The toggle mechanism 86 comprises a pair of links 92 and 93 which are pivoted together and the region of the pivotal connection is mounted in a slide 94 which moves transversely under the action of the operating rod 87. It will be seen that the travel of the toggle arms is limited on the one side by the interior of the housing at 95 and on the otherside by the portion 96 of the slide which prevents the toggle mechanism 86 from going over dead centre.

The lower toggle link 92 acts on the inner slide 83 and the member carrying the surface 96 has a shoulder 97 which urges upwardly a portion 98 of the upper end of the outer slide 82, against the action of the spring so as to pull the bush upwardly.

The operating rod 87 is pivotally linked to the upper end of a rocking lever 99 carried in hearings on a fixed mounting bracket 100. An integral extension 101 of the rocking lever 99 carries a cam roller 102 whilst a further cam roller 103 is carried by the rocking lever 99. These two rollers 102 and 103 are acted upon by a pair of cams on the shaft 26 to cause timed rocking movement of the lever 99 back and forth and hence to cause 

1. A heading machine for producing headed blanks from wire, the machine comprising: a fixed frame; a ram reciprocable in the frame; a punch carried by the ram; a die block rotatably mounted on the frame and having a plurality of die cavities capable of being indexed between a plurality of stations including a cut-off station and a blow station; feed means for feeding the wire stock intermittently directly into a die cavity positioned at the cut-off station, the feed means comprising a pair of opposed linear gripper means which cam embrace and grip the wire over a substantial length thereof and mounted on a block drivable slidably in a direction longitudinally of the fixed frame by drive means, one gripper means being secured to a lever pivoted on said block and being resiliently biased away from the other gripper means, the feed means also including a cam member having a longitudinal cam face comprising a pair of spaced planar surfaces generally parallel to the direction of feed of the wire stock and a ramp between the planar surfaces, the lever having a part adapted to co-operate with the cam face, whereby, as the block is moved forwardly by the drive means, the cam urges the lever and hence said one gripper means against the resilient bias towards the other gripper means until said co-operating part contacts the ramp whereupon said one gripper means is resiliently urged away from the other gripper means by the resilient biasing means; and a cut-off mechanism being provided adjacent the cut-off station and acting upon the wire stock to sever a blank therefrom.
 2. A heading machine according to claim 1 wherein the wire cut-off mechanism comprises, in combination, a wire supporting bush through which the wire is freely fed and which is located adjacent the die at the cut-off station, and an open knife located between the bush and the die and spaced from the face of the die, operation of the cut-off mechanism urging the knife and the bush in opposed directions to sever the wire stock and leave a blank in the die with a portion of the blank projecting from the die.
 3. A heading machine according to claim 1 wherein said shaft carrying the cam is slidably supported in the machine and is provided with means for adjusting its position in a longitudinal direction relative to the direction of travel of the gripper means whereby the position of the ramp may be adjusted to adjust the length of forward feed of wire stock by the gripper means.
 4. A heading machine according to claim 1 wherein an ejector mechanism is associated with the die assembly, each die having a respective ejector rod, each ejector rod being slidably mounted in a common mounting member and being spring urged rearwardly to bring a fixed projection on the rod into load transmitting relationship with the mounting member, the mounting member being capable of fore and aft rectilinear adjustment relative to the die block into which the ejector rods extend. 